HotMix Asphalt and Flexible Pavement Design: the MEPDG

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Hot-Mix Asphalt and Flexible Pavement Design the
MEPDG

• Kevin D. Hall, Ph.D., P.E.
• Professor and Head, Dept. of Civil Engineering
• University of Arkansas
• Flexible Pavement Research Symposium
• Denver, Colorado -- February 18, 2009

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The Plan for Today

• A Stroll Down Memory Lane(where weve been)
• A Look Up the Road(where were going)
• A Peek at Arkansas MEPDG Efforts(how we are
  trying to get there)

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Memory Lane the AASHO Road Test (late 1950s)
(AASHO, 1961)
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Memory Lane AASHTO Pavement Design (Current
1993 Edition)
Flexible pavement design the answer is
structural number (SN)
Then you break SN into layers SN (aACHM
dACHM) (abase dbase)
The design is layer thickness
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Looking Ahead M-E Pavement Design
Level 1 I know a lot about this input Level 2
I know some about this input Level 3 I know
very little about this input
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Looking Ahead MEPDG

• Distress Prediction Models
• Fatigue Cracking
• Rutting
• Thermal Cracking
• IRI

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Looking Ahead National MEPDG Efforts

• FHWA Design Guide Implementation Team (DGIT)
• NCHRP
• 1-37 Development of M-E Design Guide
• 1-39 Traffic Data Collection, Analysis, and
  Forecasting
• 1-40A Independent Review of MEPDG
• 1-40B User Manual and Local Calibration Guide
• 1-40D Technical Assistance to NCHRP 1-40A
• 1-41 Models for Predicting Reflection Cracking
  of HMA Overlays
• 1-42A Models for Predicting Top-Down Cracking
  of HMA
• 1-47 Sensitivity Analysis of the MEPDG
• 9-30 Experimental Plan for Calibration
  Validation of HMA Performance Models
• 9-30A Calibration of Rutting Models for HMA
• 9-44 Development of Work Plan for Validating
  Endurance Limit for HMA
• Lead States activities

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A Quick Peek at Arkansas Efforts
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• Sensitivity Analyses
• Materials Inputs
• HMA Dynamic Modulus
• Unbound (Soil Aggregate) Resilient Modulus
• Traffic Inputs
• Design Studies
• Local Calibration
• Database / Support Software Development
• Section I.D.
• Data Collection
• Analysis

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Arkansas Dynamic Modulus (E)

• Level 1 Catalog
• Validation of Level 3Prediction Models

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Arkansas Dynamic Modulus (E)
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Arkansas Binder (DSR)
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Arkansas Traffic
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Arkansas Database Development
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Arkansas HMA Database

• HMA Design
• Binder Conventional
• Brookfield
• DSR
• Mixture Properties
• Dynamic Modulus
• Creep Compliance
• Indirect Tension

• Construction
• Core Thickness
• Bulk Gravity
• Max Gravity
• Binder Content
• Binder Grade
• Volumetrics
• Aggregate Gradation
• Compaction

• HMA Performance
• Cracking
• Rutting
• IRI
• Other
• FWD/GPR Tests
• Friction Results
• Maintenance
• Crack Sealing
• Patching
• Seal Coats
• Milling
• Overlay

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Arkansas MEPDG Calibration
NCHRP 1-40 Recommended Practice for Local
Calibration of the Mechanistic-Empirical Pavement
Design Guide
The calibration and validation of the
performance prediction model is a mandatory
stepto establish confidence in the design and
analysis procedure and facilitate its acceptance
and use. Calibration the mathematical process
through which total (residual) error the
difference between observed and predicted values
of distress is minimized. Validation the
process to confirm that the calibrated model can
produce robust and accurate predictions for cases
other than those used for model calibration.
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Arkansas MEPDG Calibration

• Select Hierarchical Input Level for Each Input
  Parameter
• Develop Experimental Design and Matrix
• Estimate Sample Size for Each Distress Model
• Select Roadway Segments
• Extract and Evaluate Roadway Segment/Test Section
  Data
• Conduct Field Investigations of Test Sections to
  Define Missing Data
• Assess Bias for the Experimental Matrix
• Determine Local Calibration Coefficient to
  Eliminate Bias of Transfer Function
• Assess Standard Error for Transfer Function
• Improve Precision of Model modify coefficients
  and exponents of transfer functions
• Interpretation of Results decide on adequacy of
  calibration coefficients

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Arkansas MEPDG Calibration

• Sample size (minimum)
• Distortion (total rutting or faulting) 20
  roadway segments
• Load-related cracking 30 roadway segments
• Non-load-related cracking 25 roadway segments
• Reflection cracking (HMA only) 15 roadway
  segments
• Roadway Segment / Condition Surveys
• At least 3 condition surveys available for a
  roadway segment
• Condition surveys cover at least 10 years
• Increased number of surveys for higher levels of
  distress
• Range of distress magnitudes minor to close
  to design criteria
• Distress definitions/measurements consistent with
  MEPDG(Data Collection Guide for Long Term
  Pavement Performance)

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A Long-Term Effort???
THANK YOU !!!